The present invention relates generally to techniques that sense thermal stimuli. In particular, implementations employ thermal sensors with resistivity that varies in response to thermal stimuli. Such sensors can be used, for example, in a calorimeter, a term used herein to refer to any device or apparatus that measures quantities of absorbed or evolved heat or determines specific heats; the use of a calorimeter is referred to herein as calorimetry.
Calorimetry can measure enthalpic changes, including enthalpic changes arising from reactions, phase changes, changes in molecular conformation, temperature variations, and other variations of interest that may occur for a particular specimen. By measuring enthalpic changes over a series of conditions, other thermodynamic variables may be deduced. For example, measurements of enthalpy as a function of temperature reveal the heat capacity of a specimen, and titrations of reacting components can be used to deduce the binding constant and effective stoichiometry for a reaction.
Various resistive thermal sensors have been proposed for use in calorimetry. U.S. Pat. Nos. 3,467,501; 4,298,392; 5,312,587; and 4,021,307 describe calorimetric techniques employing thermistors. U.S. Pat. Nos. 5,265,417 and 5,451,371 describe calorimetric sensors with metallic resistors, such as platinum.
Previous techniques in sensing or detecting heat or temperature have a number of limitations. It would be advantageous to have additional techniques for resistive thermometer elements or resistive thermal sensors such as thermistors. In particular, it would be advantageous to have techniques that could be used in very sensitive calorimetry.